#include<stdio.h>
#include <vector>
#include <list>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <algorithm>
#include <sstream>
#include <iostream>
#include <string>

using namespace std;

int main() {
	
	long long F[3], N;

	cin >> F[0] >> F[1]>>N;

	F[2] = F[0] ^ F[1];

	cout << F[N%3] << endl;

	return 0;
}